1. Field of the Invention
The present invention relates to a flat screen type color Cathode Ray Tube (hereinafter, CRT), and particularly, a panel for a flat screen type color CRT coupled at a front portion of a funnel, for reproducing a color image.
2. Description of the Background Art
Generally, a flat screen color CRT, as shown in FIG. 1, includes a panel 1, funnel 2 and an electron gun 3.
A fluorescent layer 4 made of fluorescent material in the form of red, green and blue stripes or dots is formed on an inner surface of the panel 1, and a shadow mask 5 which functions as a color selection electrode is positioned at the rear side of the fluorescent layer 4.
A funnel 2, a vacuum bulb, is connected at the rear side of the panel 1, and at a neck portion of the funnel 2, an electron gun 3 is mounted for scanning electron beams B. A deflection yoke 6 is installed on the circumferential surface of the neck portion.
A main frame 7 made of metallic material in a rectangular form connecting the panel 1 and a shadow mask 5, and a spring 8 are installed inside the panel 1 and the funnel 2, and an inner shield 9 is fixed to the main frame 7 to shield against the influence of external magnetic fields.
The flat screen CRT displays a picture image when the electron beams B, are deflected in the horizontal and vertical directions by the magnetic fields of the deflection yoke 6, and impinge upon the fluorescent layer 4 formed inside the panel 1, emitting fluorescent light.
In the flat screen CRT, wherein the internal parts are constructed to maintain a high-degree vacuum, and as the flat screen CRT can be damaged easily by external impact, the panel 1 is designed to have a sufficient strength capable of withstanding atmospheric pressure and external impact.
Also, the flat screen CRT is provided with a reinforcing band formed on the circumferential surface of the skirt portion of the panel 1, and accordingly, the flat screen CRT is constructed to have a sufficient impact resistance by dispersing stress received by the CRT under a high-degree vacuum.
A conventional flat screen CRT is made by joining the parts of the bulb composed of the panel 1 and the funnel 2 through an exhausting process after installing the electron gun 3 at the neck portion of the funnel 2.
At this time, the panel 1 and the funnel 2 are put under considerable tension and compressive force as the interior volume is evacuated during manufacturing. Accordingly, in case an excessive tension stress is generated in a certain location of the panel 1, and an impact occurs at a portion undergoing excessive tension stress, there is a problem as the risk of the CRT imploding is increased,
Particularly, as current flat screen CRTs become large-sized, the inner and outer surfaces of the panel 1 are being made more flattened, as a result of the flattening tendency of the inner or outer surfaces of the panel 1, the implosion proof characteristic of the panel 1 is relatively weakened.
Therefore, to sufficiently maintain the implosion proof characteristic of the panel 1, the panel 1 should be made thick. However, there is a problem in that the luminance is decreased thereby and to increase the luminance, the thickness of the fluorescent material on the inside should be increased if the panel 1 is made thicker in a screen effective area.
Also, to increase the thickness of the fluorescent layer, in the limited effective surface area, a black matrix BM separating the portions of fluorescent material is formed to have a narrow width, causing a problem of deteriorated color purity.
An object of the present invention is to provide a panel for a flat screen type CRT capable of reducing the risk of damage during in the heating process in manufacture by increasing the size of the screen effective surface in accordance with the increasing of the degree of vacuum of the panel, which overcomes the problems encountered in the conventional panel for a flat screen type CRT.
To achieve the above object, the panel for a flat screen type CRT in accordance with the present invention includes an internal curvature portion within which a screen effective surface area is formed, and a skirt portion, for being connected to a funnel being extended rearwardly from the edge of the internal curvature portion; and wherein, when a radius of curvature at the inner side of the corner from the skirt portion to a sealing edge portion therein is Rs, and the radii of blend curvature of a long-side portion, a short-side portion, and a corner portion in the part where the internal curvature portion and skirt portion meet are Rx, Ry, and Rd respectively, the equations of 0.4 less than Rd/Rs less than 0.6, 1xe2x89xa6Rx/Rdxe2x89xa64, and 1xe2x89xa6Ry/Rd xe2x89xa62 are satisfied.